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Dissertation/Thesis Abstract

An Observational and Experimental Analysis of Eelgrass and Its Epifaunal Community in Bodega Harbor, California
by Ha, Grace, Ph.D., University of California, Davis, 2019, 126; 22624117
Abstract (Summary)

Seagrass — marine flowering plants that create underwater meadows through-out temperate and tropical coastal waters — are important foundation species, acting as key nursery grounds for many commercial and recreational fisheries, performing ecosystem functions including flow modification and sediment stabilization, and providing habitat to diverse and productive communities of marine life. Given the de-cline of seagrass globally, there is particular need for documenting and understanding the dynamics of seagrass ecosystems.

Focusing on the eelgrass (Zostera marina L.) beds of Bodega Harbor, Califor-nia, USA, I approached this task through methods that incorporated natural history, field research, statistical analysis, and taxonomy. In Chapter 1, I conducted a 16-month survey of eelgrass and its epifauna and analyzed species abundances in the context of the extreme warm-water event known as “The Blob” that occurred along the Califor-nian coastline in 2014. My research found a diverse invertebrate assemblage compris-ing mostly native detritivore-grazers, which contrasted sharply with nearby San Fran-cisco Bay, which has been dominated by invasive species. Invertebrate population dynamics correlated closely to that of the eelgrass they inhabited, and in general, both habitat and epifauna declines coincided with increasing seawater temperatures.

In Chapter 2, I used eelgrass as a model system to test the role of camouflage in predator-prey interactions. I conducted field experiments, testing whether prey survival was affected by color-matching between prey and habitat, using the green amphipod, Ampithoe lacertosa and artificial habitats made of eelgrass, and clear, red, and green plastic ribbon. With seine nets and underwater video recordings, I also collected data on fish predator abundance and diversity. Although generalized linear regressions in-dicated habitat color significantly affected prey survival, greater color-matching did not predict greater prey survival. Further analysis using structural equation modeling indi-cated that the effect of habitat on prey survival was significantly mediated by fish densi-ty and, to a lesser degree, fish diversity. Even after taking these effects into account, I did not find survival to clearly correspond to increasing color-match between prey and habitat. These results were consistent with the equivocal conclusions of previous stud-ies on the anti-predator hypothesis of camouflage, altogether suggesting further theory development and experimentation is needed to explain the frequency of apparent camouflage in nature.

In Chapter 3, I described a new species of porcellidiid copepod — found during the epifaunal surveys I conducted in 2013-2014. This was the first porcellidiid copepod species to be described from North America, although porcellidiid copepods have been previously recorded in Northeast Pacific coastal surveys. Porcellidium species nova n. sp., can be distinguished by a deep cleft in the female genital double somite, a lack of plumulose setae and three coupling denticles (two bulbous denticulate pads and one smooth protrusion) on the male antennule, and clear coloration with pur-ple/maroon bands across the first and last metasomes. I have provided a partial revi-sion to a key to Porcellidium species, along with a discussion of the natural history and distribution of porcellidiid copepods along the Northeastern Pacific coastline.

Indexing (document details)
Advisor: Sanford, Eric, Williams, Susan L
Commitee: Wainwright, Peter, Gaylord, Brian
School: University of California, Davis
Department: Ecology
School Location: United States -- California
Source: DAI-B 81/8(E), Dissertation Abstracts International
Subjects: Ecology
Keywords: Camouflage, Eelgrass, Epifauna, Extreme warming, Natural history, Zostera marina
Publication Number: 22624117
ISBN: 9781658412452
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